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Message |
    
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 301
Registered: 4-2006
| | Posted on Sunday, April 08, 2007 - 9:36 pm: | 
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OK, so 108" is considered 1/4 wave correct? and even antennas with coils are considered 1/4 wave correct? They use this coils to reduce the overall length correct? OK, now that we have that established, are there any 1/2 wave mobile antennas out there with coils or any other scheme to reduce their overall length? |
Ikei
New member
Username: Ikei
Post Number: 6
Registered: 3-2007
| | Posted on Monday, April 09, 2007 - 12:06 am: |
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Try Everhardt antennas. I have several in 4 and 5' size. I get good performance on 10 and 11 meters using my Magnum s980. Do a Google search. |
Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 177
Registered: 9-2004
| | Posted on Monday, April 09, 2007 - 8:50 am: |
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I bought an Everhardt antenna a few weeks ago ,all I can say is woooooooww!! It performs great, 68 inches overall length,swr is great and the magnet holds on very well,now when i get the amp installed it should be a great combo.
Bob CEF451
Robert L. Spicer
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Tech833
Moderator
Username: Tech833
Post Number: 1649
Registered: 8-2002
| | Posted on Monday, April 09, 2007 - 10:59 am: |
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Copper Night Sticks and Firestiks are coil loaded 5/8 (and one 7/8) wave antennas. They do NOT outperform a full length 108" whip. Physical length is more important than wire length when you coil it up. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3600
Registered: 7-2004
| | Posted on Monday, April 09, 2007 - 12:04 pm: |
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davemade used to make a 1/2 wave mobile, 'the rod of god', a HUGE piece of metal, with a coil the size of a tree trunk in the middle. the OLD 25k coiled antenna i had back in the mid 80's performed EXACTLY the same, & i didn't fear getting blown upside down in high crosswinds while driving at 70 mph. the pic is still on the nc site. |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 304
Registered: 4-2006
| | Posted on Monday, April 09, 2007 - 2:34 pm: |
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Pat, I am asking because I plan on doing the multiple antenna thing on my van. You had mentioned that 1/2 wave would be better than 1/4 wave. Any idea on the spacing inbetween each antenna? |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3603
Registered: 7-2004
| | Posted on Tuesday, April 10, 2007 - 4:59 pm: |
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james, 1/2 wave (or 5/8 or .64) at a base, 1/4 wave (with vehicle roof as ground plane) on a car. at 27 mHz at least, due to size constraints. google....all kinds of antenna related words-yagi, beam, how to build..., etc. you will get dimensions for EVERYTHING. look at pics on some of the custom ampbuilders sites, bigradios.com, etc & you'll get some ideas. the rest is experimentation with each particular case. a local (who i haven't seen in 2 years now) had a wagon with a predator on it. he put dual predators on it-cophased. he had a dx1600 that he claimed was doing 2kw+. my wattmeter DID show 2kw+, but it PEGGED my reflect meter real hard. needless to say, he couldn't get out locally or DX to save his life. we tried a whole bunch of things while sitting by the water in oakdale-ALL trial & error. new coax, rear antenna 'hot', 1.1:1 SWR, barely moving the reflect meter, front antenna approx 6' forward, grounded to roof & a couple inches shorter then rear/hot antenna, SWR still 1.2 or 1.3:1, dx1600 showing just over 1kw PEP, with less then 20 watts reflect, WAY directional to the front of the car, & was GOOD! he WAS a big boy....til he disappeared. |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 313
Registered: 4-2006
| | Posted on Tuesday, April 10, 2007 - 8:33 pm: |
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Yeah. I did a ton of searches for different terms "mobile beam" "Spacing betwen antennas" "How to build a mobile beam", etc... Yes, I saw pictures, saw the 'big boys', the keydowns, channel 6 guys, etc... but nothing specifically stating the space inbetween each antenna.
I think I am realizing now that there is no definite answer, but rather unique in each case, I was at the least hoping to get a ballpark number of the length inbetween each antenna on the roof though. maybe i'll just stick to my original plan, and throw the imax 2K with the GPK up there. I'll have quick release on the radials for the GPK, and a quick release for the top whip of the actual antenna. I'll have it mounted on a 5 foot mast, cut a hole in my roof and slide it through into a spare tire to keep it centered. |
Vanillagorilla
Advanced Member
Username: Vanillagorilla
Post Number: 993
Registered: 4-2005
| | Posted on Tuesday, April 10, 2007 - 8:39 pm: |
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....til he disappeared.
Ummmm....gulp 
Hank~CEF559/CEFHAM242
11mtr Northeast Net Control
Eastern Long Island NY
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